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Appendix II.

915

and the  next figures compare working cost   of various power-
producers.

COMPARATIVE COST OF ONE I.H.'P. HR.

Steam    ...        ...    \d.

(Lighting) .    \d. to \d.

Gas

\ (Poor)

\d. or less.

Petroleum         ...        ...    \d.

Electricity (from main) ...    2d.
Hydraulics (from main)...  i\d.

P.   7<9p.    Oil   Engines.—For   motor-cars   the   Priestman

•engine was too heavy, so Daimler and others designed lighter forms,
Fig. 878. There were two cylinders, side by side, having cranks
at 180°, and using the Otto cycle, so there was an explosion per
revolution. The charge of oil-vapour and air entered at A, the
exhaust leaving at B ; and the ignition tube c, of platinum, was
kept hot with a lamp. The oil, benzoline, flowed from reservoir
R through the chamber r>, at a slow and regular rate, controlled
by float E, and as it emerged at F was wafted into spray by the
suction air at a The exhaust-valve B was lifted every second
revolution by a cam j, worked from crank shaft by gearing.
Further information on motor-cars and their details is given in
the Appendices at pp. 947, 965, 999, and 1182.

Hot-air Engines.—These are sufficiently illustrated by the